Test Background C1 inhibitor deficiency causes hereditary angioedema (HAE). Patients present with acute deep tissue oedema, typically of the face, larynx or abdomen, which can be life threatening if respiratory obstruction occurs. 85 % of HAE patients have low antigenic C1 esterase inhibitor levels (type I HAE). The C4 level is low, especially during attacks. Request alongside C3 and C4 levels, plus C1 functional activity.
Clinical Indications Recurrent angioedema, laryngeal oedema, or abdominal pain in the absence of urticaria Family history
Reference Range 0.22-0.38 g/L
Sample Required RST (rust top) Separate and freeze immediately Transport frozen
Sample Volume 5-10 mL (1 mL serum)
Turnaround Time 21 days
Notes This test is currently unaccredited due to a change in platform